Role of stress hormones and the amygdala in creating lasting memories

Abstract

Over a century ago, William James asked a critical question that continues to guidecurrent memory research: "Of some [experiences] no memory survives the instanceof their passage. Of others, it is confined to a few moments, hours or days. Others,again, leave vestiges that are indestructible, and by means of which they may berecalled as long as life endures. How can we explain these differences?" (James1890 p 643). Interestingly, Descartes proposed an answer to James' question overtwo centuries earlier when he wrote: "The usefulness of all of the passions consistsin their strengthening and prolonging in the soul thoughts which are good for it toconserve" (Descartes 1650). Findings of animal as well as human studies reviewedin this chapter provide extensive evidence supporting Descartes' hypothesisand have revealed neurobiological processes mediating the "strengthening and prolonging"of memories of significant experiences (McGaugh 2004). Emotionally significantexperiences activate hormonal and brain systems that regulate the consolidationof newly acquired memories. These effects are integrated through noradrenergicactivation of the basolateral amygdala, which regulates memory consolidationvia interactions with many other brain regions involved in consolidating memoriesof recent experiences (McGaugh 2002, 2004). Thus, the activation of these stresshormone and brain systems enable significant experiences to become well remembered;perhaps as James noted, "as long as life endures" Moreover, intense orexcessive activation of these systems may, as Pitman (see the chapter by Pitmanthis volume) has suggested, play a critical role in the etiology of posttraumaticstress disorder (PTSD).